Diaper rash is a common form of irritation and inflammation of those parts of an infant's body normally covered by a diaper. It frequently occurs also in areas immediately adjacent to the diapered area. This condition is also referred to as diaper dermatitis, napkin dermatitis, napkin rash, and nappy rash. While certainly more common in infants, this condition is not, in fact, limited to infants. Any individual who suffers from incontinence may develop this condition. This ranges from newborns, to the elderly, to critically ill or nonambulatory individuals.
It is generally accepted that true "diaper rash" or "diaper dermatitis" is a condition which is, in its most simple stages, a contact irritant dermatitis. The irritation of simple diaper rash results from extended contact of the skin with urine, or feces, or both. Diapers are worn to catch and hold the body waste, but generally hold the waste in direct contact with the skin until changed, i.e., in occluded fashion for long periods of time. The same is true for an incontinence pad, or incontinence brief. However, while it is known that the body waste "causes" diaper rash, the precise component or components of the urine or feces which are responsible for the resulting irritation of the skin have not been conclusively identified. The most commonly accepted list of factors linked to diaper rash includes ammonia, bacteria, the products of bacterial action, urine pH, Candida albicans, and moisture. These are generally cited in the art as being the most likely candidates for agents or conditions which product or aggravate diaper rash.
It has now been discovered that a primary cause of diaper rash is a particular set of conditions which arises as a result of prolonged contact of skin with mixtures of feces and urine. Activity of proteolytic and lipolytic fecal enzymes present in such a mixture is believed to be a major factor in producing skin irritation. Urine in contact with enzymes from feces can also result in production of ammonia which raises skin pH. This rise in skin pH, for example to levels of 6.0 and above, in turn increases that fecal proteolytic and lipolytic enzymatic activity which produces diaper rash. Urine itself can also contribute to diaper rash by adding moisture to the diaper environment. Water, and particularly water in the form of urine, is especially effective at diminishing the barrier property of skin, thereby enhancing the susceptibility of skin to fecal enzyme irritation.
The foregoing diaper rash model suggests that effective diaper rash control can be achieved by lowering skin pH to values well within the acidic range to inhibit irritation-producing enzymatic activity while simultaneously maintaining the diaper environment as dry as possible. Lowering of skin pH may also be an important factor in providing rash or odor control in other types of absorbent articles such as sanitary napkins.
Articles, compositions and procedures which inherently tend to lower the pH of diapered skin are known in the art. In fact, a number of prior art references teach the addition of various acidic pH control or "ammonia-absorbing" agents to absorbent articles or to the diapered skin environment. Such references include, for example, Alonso et al., U.S. Pat. No. 4,382,919, Issued May 10, 1983; Blaney, U.S. Pat. No. 3,964,486, Issued June 22, 1976; Bryce, U.S. Pat. No. 3,707,148, Issued Dec. 26, 1972; and Jones, Sr., U.S. Pat. No. 3,794,034, Issued Feb. 26, 1974.
In those instances in the prior art wherein acidic pH control agents have been icorporated into the cores of absorbent articles, significant amounts of acid are needed in order to bring about the desired "absorption" of ammonia or lowering of skin pH. Protons released by acid material in an absorbent structure core must be carried to the skin by the relatively inefficient mechanism of back diffusion or re-wetting of the skin with fluid such as urine. In those instances wherein acidic material is carried on or in topsheets of prior art absorbent articles, the character or "feel" of such topsheets may be made undesirably altered by the presence of coated or impregnated acid. In addition, acidic material from such topsheets may be leached or abraded from the topsheet and delivered to the skin in a form which might cause undesirable comfort or safety problems.
In view of the foregoing it can be seen that there is a continuing need to identify improved disposable absorbent articles which are effective for absorbing discharged body waste and which also provide a desirable skin pH control benefit. The improved absorbent articles hereinafter described have such absorbency and skin pH control characteristics.